Audacity is a free, easy-to-use audio editor and recorder for Windows, Mac OS X, GNU/Linux, and other operating systems. Use it to edit your sounds using Cut, Copy and Paste (with unlimited Undo), mix tracks together, or apply effects to your recordings.
Audacity also has a built-in amplitude envelope editor, a customizable spectrogram mode and a frequency analysis window for audio analysis applications. Built-in effects include Bass Boost, Wahwah, and Noise Removal, and it also supports VST plug-in effects.

Audacity is an audio tool that allows you to record and play sounds, import or export WAV, AIFF or MP3 files.

Audacity supports all common editing operations, plus it will mix tracks and let you apply plug-in effects to any part of a sound. It also has a built-in amplitude envelope editor, a customizable spectrogram mode and a frequency analysis window for audio analysis applications.

You can use Audacity to:
* Record live audio.
* Convert tapes and records into digital recordings or CDs.
* Edit Ogg Vorbis, MP3, and WAV sound files.
* Cut, copy, splice, and mix sounds together.
* Change the speed or pitch of a recording.
* Import and export WAV, AIFF, AU, and Ogg Vorbis files.
* Import MPEG audio (including MP2 and MP3 files) with libmad.
* Export MP3s with the optional LAME MP3 encoder library.
* Create WAV or AIFF files suitable for burning to CD.
* Import and export all file formats supported by libsndfile.
* Open raw (headerless) audio files using the “Import Raw” command.
* And more!

Audacity 2.0.0 was released on 13 March 2012:
These Release Notes describe:
* Changes in 2.0.0 as compared with 1.3.14
* Summary of bug fixes and new features between 1.2.6 and 2.0.0
* Issues with 2.0.0 which were known at time of release
Contents:
1 Changes between 1.3.14 and 2.0.0
1.1 Bug fixes
1.1.1 Interface
1.1.2 Imports and Exports
1.1.3 Effects and Analysis
1.1.4 Other miscellaneous bug fixes
1.2 Changes and Improvements
2 Summary of bug fixes and new features between 1.2.6 and 2.0.0
2.1 Bug Fixes
2.2 New features
3 Known Issues at Release
3.1 Headline issues
3.1.1 Large Projects
3.1.2 Problems reopening, saving or crashing in projects
3.2 Changes and Improvements
3.3 Program Launch
3.4 Installation
3.5 Imports and Exports
3.6 Interface
3.7 Playback and Recording
3.8 Effects and Analysis
3.9 Projects
3.10 Accessibility
3.11 Chains
3.12 Clips
3.13 Compiling
3.14 Label Tracks
3.15 Mixer Board
3.16 Preferences
3.17 Toolbars
3.18 Miscellaneous platform-specific issues
3.19 Bugs requiring more investigation